Historians do not think like lawyers. Colonial Whigs frequently did. The
constitutional theory of the American Revolution has never been given the credit
it deserves. This is the thesis in John Phillip Reid, In defiance of the law
(Chapel Hill, 1981). and I have borrowed heavily from his text in this page.
This page comments on the constitutional arguments of the revolutionists.

It is not known generally today by academic historians that in 1770, the
English "Constitution" did not mean what it does today. Today the
English Constitution is known as whatever Parliament says it is. Not so in 1750,
according to many lawyers on both sides of the Atlantic. Valid legal arguments
were made that the English Constitution was a unwritten system of customary
restraints on what the King and the governing body could do.

Consider Lord Camden. In 1766, he was Chief Justice of one of the central
common law courts and about to become Lord Chancellor.. At that time he warned
Parliament that there were steps, including taxing the American Colonies, that
it could not take legally. Camden agreed with the theory of the Massachusetts
lawyers: that the English Constitution was a system of customary restraints on
what the King and the governing body could do. And that customary restraint made
it legally improper to tax without the consent of the representatives of the
English persons to be taxed. Lord Camden, "House of Lords Debate of 10 Feb
1766," in Parliamentary History (1766), 168.

It is necessary for us to understand that the constitutional case of 18th
Century American lawyers and Whigs was based on the same unwritten constitution
that 17th Century English lawyers and Whigs had used to attack Charles I and
James II. In fact an English writer could say in 1768, "The late unhappy
Stamp Act made here, to operate in America, was certainly as unconstitutional a
measure as King James II's dispensing power." "Stamp Act is
unconstitutional," in Gentlemen's Magazine (1768), 356.

For example, Oliver Saint-John, Solicitor General of England, in 1641, before
the English Civil War commenced, told the Lords that the law could not proceed
in subversion of the unwritten constitution. Oliver Saint-John, "Argument
of Law," (1641), 20.

After the glorious Revolution of England John Toland wrote, in 1701
"Parliament neither has nor ought to have an arbitrary power over the
lives, liberties, or fortunes of the subjects, and should they manifestly appear
to aim at such an execrable design, the whole people may justly call them to
account." Toland, Anglia Libera. 4.

When the British put a standing British army in the colonies, and defended
the constitutionality of their standing army in America on the grounds that it
was sanctioned by Parliament — American lawyers thought in terms of 17th
Century English theory. The American colonists, in the 1700's, found their
constitutional arguments in the arguments of Sir Edward Coke, John Hampden, and
John Pym. Americans, and also some English, took the position that a
standing army was unconstitutional in the colonies. The Americans argued that
Parliament alone could not give a standing army constitutional sanction. 18th
Century Americans

The Imperial Army in America was a constitutional violation, according to the
American lawyers. American lawyers were appealing not to a political theory of
what should be; they appealed to what they regarded as a British customary
constitution that ordained the legally permissible. Consider a speech of Lord
Chancellor Hardwick, to the House of Lords in 1756 3 in which he stated "A
standing army in time of peace, execution of Martial Law in a time of peace, are
against law." Lord Chancellor Hardwick was not only the Lord Chancellor at
the time he spoke but he had been Chief Justice of the King's Bench, privy
counselor, Solicitor General of England and a Bencher of Lincoln's Inn. He was
there for one of the most prominent common law lawyers of the Century. In short,
to the extent that Chancellor York was speaking generally, Chancellor York
agreed with the Massachusetts lawyers' argument that the use of British troops
as a standing army available "at home" to the home
government was an unconstitutional use of force. Lord Chancellor Hardwick,
"Lords Debates of 24 May 1756," in Parliamentary History (1756).
[But England in 1756 was starting to distinguish between the home island of
England and the "conquered lands" which they said did not have the
rights of the home island.]